Fireplace unity with thin rear firebox wall

ABSTRACT

A fireplace unit adapted for permanent, fully enclosed installation wherein the rear wall of the firebox or combustion chamber is of thin, sheet metal. Passageways are provided outside the combustion chamber for the flow of cooling air to substantially eliminate the possibility of damage to the rear wall due to the intense heat concentrated thereon.

United States Patent 1 Andrews [111 3,744,477 [451 July 10,1973

l l FIREPLACE UNITY WITH THIN REAR FIREBOX WALL [75] Inventor: [73]Assignee: Vega Industries, Inc., Syracuse, NY. 22 Filed: Oct. 12,1971

21 App]. No.: 188,052 i George M. Andrews, Syracuse, NY.

[52] US. Cl. l. 126/120 [51] Int. Cl. F24b l/l8 [58] Field of Search126/121, 120

[56] References Cited UNITED STATES PATENTS 3,664,325 5/ 1972 Malafouris1261121 3, I 90,28l 6/1965 Northwood 126/120 3/1964 Northwood et a]126/120 Primary ExaminerWilliam F. ODea. Assistant Examiner- HaroldJoyce Att0mey-F. P. Keiper et al.

[5 7] ABSTRACT A fireplace unit adapted for permanent, fully enclosedinstallation wherein the rear wall of the firebox or combustion chamberis of thin, sheet metal. Passageways are provided outside the combustionchamber for the flow of cooling air to substantially eliminate thepossibility of damage to the rear wall due to the intense heatconcentrated thereon.

7 Claims, 8 Drawing Figures 1011966 Rose l26/l21 SHEU 1 BF 5 INVENTOR.

BY \WBELML ATTORNEY PATENmJunms-n SHEEI 2 0? 5 vi N? mm INVENTOR.

ATTORNEY PATENIiniuumsza 3.744.477,

I saw a or s FIG.

I N VEN TOR.

BY QMSF ATTORNEY PAIENIED JUL I 01913 SEEEHHIS ATTORNEY FIREPLACE UNITYWITH THIN REAR FIREBOX WALL The present invention relates toprefabricated fireplace units and, more particularly, to a constructionof such units wherein the rear wall of the combustion chamber may be ofa relatively light gage metal.

In all conventional fireplace constructions the area of highest heatconcentration is the rear wall of the combustion chamber. This is due tothe fact that as the air within the combustion chamber is heated andrises through the flue, additional air is drawn in through the openfront of the fireplace, passing over, around and under (when the usualgrate is provided) the flames in a rearward direction and thence up therear surface of the combustion chamber. It has therefore been necessaryto construct the rear wall of materials which can withstand very hightemperatures without damage which would require frequent repair orreplacement. This is the case with sO-called prefabricated orfactorybuilt fireplaces which are installed in a permanent manner (i.e.fully encased with little or no clearance to combustible material), aswell as those which are constructed integrally with the building. Thatis, while some free-standing room fireplaces of a decorative typeintended to enclose only relatively small fires may be constructed oflighter, less durable materials, the permanently encased fireplace hasrequired a rear wall of refractory material, or heavy steel plate.

The present invention has as a principal object the provision of apermanently installed fireplace which may have a relatively light gagesheet metal as a rear wall for the combustion chamber. This is madepossible through the novel construction disclosed herein, which ensuresthat a sufficient amount of cooling air will be directed over the rearor inner surface of the rear wall to offset the intense heat on theforward surface sufficiently to prevent damage. This has the obviousadvantage of eliminating the heavy rear wall of refractory or platemetal, thus being especially advantageous in factory-built fireplaceunits by simplifying and saving on fabrication, packing, shipping andinstallation.

A further object is to provide a prefabricated fireplace structure whichmay be permanently installed with little or no clearance to combustiblematerials, a circulation system for cooling air being provided hehind,as well as in front of the rear wall of the combustion chamber.

In a more general sense, the object of the invention is to provide afireplace unit which is faster and cheaper to make and install thanprevious units of similar size and design.

The above and other novel features of theinvention will appear morefully hereinafter from the following detailed description when taken inconjunction with the accompanying drawings. It is expressly understoodthat the drawings are employed for purposes of illustration only and arenot designed as a definition of the limits of the invention, referencebeing had for this purpose to the appended claims.

In the drawings, wherein like reference characters indicate like parts:

FIG. 1 is a front elevational view of the fireplace unit of theinvention, with portions broken away;

FIG. 2 is a side elevational view in section on the line 22 of FIG. 1;

FIG. 3 is a top plan view, partly in section;

FIG. 4 is an enlarged detail of a portion of FIG. 3; FIG. 5 is aperspective view of certain elements of the unit with portions brokenaway;

FIG. 6 is an elevational view of one of the elements of FIG. 5;

FIG. 7 is a rear elevation of a portion of the unit; and

FIG. 8 is a plan view taken on the line 8-8 of FIG. 7.

As seen in FIG. 1, the exterior of the fireplace unit includes outerhood 10, comprising inner and outer layers of sheet metal enclosing alayer of insulation 12. An air space is provided between the inner layerof outer hood l0 and inner hood 14, having a system of louvers 16 in theupper portion thereof. Adjustable damper 15 is provided in the usualmanner with chain 17 having an end portion or handle manually accessibleat the front of the fireplace. The lower portion is enclosed on thefront by outer shell 18 on the top and sides of the combustion chamberopening. Upper and lower hearth covers 20'andj22, respectively, areprovided on the lower front side of the unit and cooperate to form anopening for the entry of room air, as best seen in FIG.

The unit rests on a steel frame or skid 24 and is enclosed on the bottomby sheet metal skid cover 26. A

pair of hearth supports 28 rest on skid cover 26. Hearth 30 serves asthe floor of the firebox or combusion chamber, resting on hearthsupports 28, and is formed of the usual cast refractory material. Thehearth supports are generally V-shaped in front view with the centralpart open to permit rearward flow of air through as well as around thesupports. Forward edges 32 of the hearth supports are sloped rearwardly,as shown in FIG. 2, to support lower hearth cover 22.

Wing panels 34 and liner 36 form the side and rear walls, respectively,of the combustion chamber. An embossed brick pattern on both the windpanels and liner provides a decorative effect and enhances structuralrigidity. Wing panels 34 are attached by sheet metal screws along theirforward edges to inner shell 38. The rear edges of the wind panels arebent over, as best seen in FIG. 4, to provide flange 40 which holds thewing panel apart from the inner shell, thereby absorbing the mostintense heat on a separate, more easily replaceable element rather thanthe inner shell itself. The enlarged detail of FIG. 4 also shows howliner 36 is attached to liner control shield 42, which in turn isaffixed to inner shell 38. Thus, an air space is provided between liner36 and control shield 42 and between the control shield and the rearportion of inner shell 38. A further air space is provided, as seen inFIG. 2, between inner shell 38 and the inner metal layer of outer shell44. The latter comprises inner and outer metal sheets with a layer ofinsulation therebetween, as in the structure of outer hood 10. As shownin the sectioned portion of FIG. 3, outer shell 44 extends along thesides, as well as the rear of the fireplace unit. A pair of verticallydisposed, L-shaped spacer brackets 46 (FIG. 5) are affixed to innershell 38, one on each side, at the center of the rear portion thereof,to maintain the proper spacing between the inner shell and controlshield 42 on one side,and the inner layer of outer shell 44 on the otherside.

Control shield 42 is shown separately in FIG. 6. A system of louveredopenings 48 are provided in the lower portion of the shield and aredirected downwardly toward the rear, i.e., the side facing inner shell38. A second system of louvered openings 50 are provided in the upperportion and are directed upwardly toward the rear. The louvers are notshown in FIG. 5 in order to simplify the drawing, but may be seen inFIG. 2. FIGS. 7 and 8 illustrate the attachment, preferably by welding,of three V-shaped spacers 52 to the rear surface of liner 36. Thesemaintain the proper spacing between the liner and control shield 42. Itwill be noted that the louvers of both the upper and lower groups ofcontrol shield 42 are arranged in four vertically disposed rows; theedges of spacers 52 are arranged to contact the control shield in thespaces between each row of louvers.

Referring again to FIG. 2, the air flow which maintains the temperaturesof the various elements at a satisfactory level is indicated by arrows.When a fire is started the heated air and smoke rise through inner hood14 to the chimney outlet. The air is replaced by room air drawn inthrough the open front of the fireplace. Liner 36 will thus be heatedvery rapidly since the air being drawn into the fireplace is movingrearwardly, thereby directing the flames and hottest air onto the rearsurface of the combustion chamber. The air behind liner 36 will also beheated and tend to rise. As it does so, it must pass out of upperlouvers 50 to the space between control shield 42 and inner shell 38.This air is replaced by air passing through lower louvers 48 whichenters the space between the control shield and inner shell from thebottom after passing under hearth 30. The air enters through the openingbetween upper and lower hearth covers 20 and 22. A certain amount of theair passing under the hearth will be deflected upwardly by baffle 54 tothe space between the control shield and inner shell, while anotherportion will pass under baffle 54 and rise between inner shell 38 andthe inner layer of outer shell 44. Of the air which enters the spacebetween control shield 42 and inner shell 38, a quantity sufficient toreplace the heated air which leaves the space between liner 36 and thecontrol shield via louvers 50 will enter this space through lowerlouvers 48. Additional air will continue to pass upwardly in the spacebetween control shield 42 and inner shell 38 and rejoin the air whichhas passed between the control shield and liner 36 and out of louvers50. An upper extension 55 of inner shell 38 is joined at the top andsides with inner hood 14. Louvers 56 on the rear side of the inner hoodadmit the air which has risen behind control shield 42, including thatwhich has passed between the control shield and liner 36, therebyjoining such air with the combustion products from the firebox forexhaust through the chimney.

The air which has risen between inner shell 38 and the inner layer ofouter shell 44 passes over the back of upper extension 55 of the innershell and also around the sides of inner hood 14. This air entersthrough louvers 16 for exhaust through the chimney and has a distinctcooling effect on the inner hood as it passes over the outer surfacethereof. The air entering the inner hood through louvers 56 also has acooling effect on the lower rear portion of the hood; although this airhas picked up a considerable amount of heat in passing behind the linerand control shield, it is still cooler than the air inside the hoodwhich is rising directly from the combustion chamber.

Thus, the structure and combination of the various elements provides afireplace unit which has sufficient cooling air in passageways outsidethe combustion chamber to permit the use of a relatively thin, sheetmetal rear wall. The material of liner 36 is preferably a chromium alloysteel, e.g., ASTM type 430 stainless steel, or other corrosion resistantsteel, which may be 0.020 inches in thickness. At least the rear part ofinner hood '14 is also preferably of stainless steel. It will be notedthat spacers 52 insure that the necessary space is maintained behindliner 36, when such space might otherwise be impaired by deformation ofliner 36 due to being bumped by logs, a grate, etc.

What is claimed is:

l. A fireplace unit for permanent installation and enclosure as part ofa structure, said unit comprising:

a. an open front combustion chamber having a hearth floor, side and rearwalls and a flue for exhaust of combustion products;

b. said hearth floor being raised from the supporting structure toprovide a passage for air thereunder;

c. a second wall substantially parallel to and spaced rearwardly fromsaid rear wall to define therebetween a space enclosed at the top,bottom and sides;

d. a third wall substantially parallel to and spaced rearwardly fromsaid second wall to define therebetween a space open at the bottom tocommunicate with said passage, whereby air may pass directly from saidpassage into the space between said second and third walls; and

e. means defining a plurality of openings in said second wall to allowair to pass between the space between said second and third walls, andthe space between said second and rear walls.

2. The invention according to claim 1 wherein said rearv wall isconstructed entirely of sheet metal on the order of 0.020 inches thick.

3. The invention according to claim 2 wherein said sheet metal isstainless steel.

4. The invention according to claim 1 wherein said openings in saidsecond wall are provided both near the bottom and near the top thereof,whereby a first portion of the air passing from the space under saidhearth to that between said second and third walls remains therebetweenas it is heated and rises, and a second portion of said air passesthrough the openings near the botton of said second wall into the spacebetween said rear and second walls and is heated and rises therebetweenand passes back to the space between said second and third walls throughthe openings near the top of said second wall.

5. The invention according to claim 4 and further including an innerhood disposed above said combustion chamber to enclose the combustionproducts rising therefrom, an outer hood enclosing said inner hood inspaced relation thereto, and means for directing the air which haspassed beneath said hearth into the space between said inner and outerhoods and through openings in said inner hood into the interior thereof.

6. The invention according to claim 5 wherein said second wall isdisposed below and contiguously with a portion of said inner hood, andsaid third wall extends into the space between said inner and outerhoods and is joined at the top and sides of said inner hood, wherebysaid first and second portions of air are directed into the spacebetween said inner hood and the extension of said third wall and entersaid inner hood through openings therein communicating with saidlastnamed space.

7. The invention according to claim 6 and further ina portion of the airpassing under said hearth is directed eluding a fourth wall disposed ina plane substantially into the space between said third and fourth wallsand parallel to and rearwardly spaced from said third wall, thencebetween said inner and outer hoods. and below and contiguously with saidouter hood, and

1. A fireplace unit for permanent installation and enclosure as part ofa structure, said unit comprising: a. an open front combustion chamberhaving a hearth floor, side and rear walls and a flue for exhauSt ofcombustion products; b. said hearth floor being raised from thesupporting structure to provide a passage for air thereunder; c. asecond wall substantially parallel to and spaced rearwardly from saidrear wall to define therebetween a space enclosed at the top, bottom andsides; d. a third wall substantially parallel to and spaced rearwardlyfrom said second wall to define therebetween a space open at the bottomto communicate with said passage, whereby air may pass directly fromsaid passage into the space between said second and third walls; and e.means defining a plurality of openings in said second wall to allow airto pass between the space between said second and third walls, and thespace between said second and rear walls.
 2. The invention according toclaim 1 wherein said rear wall is constructed entirely of sheet metal onthe order of 0.020 inches thick.
 3. The invention according to claim 2wherein said sheet metal is stainless steel.
 4. The invention accordingto claim 1 wherein said openings in said second wall are provided bothnear the bottom and near the top thereof, whereby a first portion of theair passing from the space under said hearth to that between said secondand third walls remains therebetween as it is heated and rises, and asecond portion of said air passes through the openings near the bottonof said second wall into the space between said rear and second wallsand is heated and rises therebetween and passes back to the spacebetween said second and third walls through the openings near the top ofsaid second wall.
 5. The invention according to claim 4 and furtherincluding an inner hood disposed above said combustion chamber toenclose the combustion products rising therefrom, an outer hoodenclosing said inner hood in spaced relation thereto, and means fordirecting the air which has passed beneath said hearth into the spacebetween said inner and outer hoods and through openings in said innerhood into the interior thereof.
 6. The invention according to claim 5wherein said second wall is disposed below and contiguously with aportion of said inner hood, and said third wall extends into the spacebetween said inner and outer hoods and is joined at the top and sides ofsaid inner hood, whereby said first and second portions of air aredirected into the space between said inner hood and the extension ofsaid third wall and enter said inner hood through openings thereincommunicating with said last-named space.
 7. The invention according toclaim 6 and further including a fourth wall disposed in a planesubstantially parallel to and rearwardly spaced from said third wall,and below and contiguously with said outer hood, and a portion of theair passing under said hearth is directed into the space between saidthird and fourth walls and thence between said inner and outer hoods.